A head lamp (front lamp) of a vehicle such as, for example, an automobile, is provided with an aiming adjustment mechanism to adjust a lamp optical axis in a predetermined angle direction in front of the automobile. As the aiming adjustment mechanism, a configuration of operating an aiming screw disposed in a lamp housing is generally adopted. For example, the aiming screw is screw-connected to at least a portion of a lamp unit equipped within the lamp housing. By operating the aiming screw to be axially rotated from the outside of the lamp unit, the screw-connected portion of the lamp unit is screwed along the axial direction of the aiming screw, and the vertical and horizontal tilting angles of the lamp unit are adjusted.
In order to operate the aiming screw to be axially rotated, a bevel gear (umbrella gear) or a crown gear is generally provided at the end of the aiming screw exposed to the outside of the lamp housing. When the tip end of a tool such as, for example, a plus driver (Phillips driver) is inserted between the bevel gear or the crown gear and the external surface of the lamp housing, and the plus driver is operated to be axially rotated so as to rotate the bevel gear or the crown gear, the aiming screw is axially rotated.
Japanese Laid-Open Patent Publication No. 2008-243604 suggests an operation unit connected to the crown gear, in order to improve the workability of the aiming screw in the aiming adjustment. The operation unit includes an operation rod which is axially rotated directly by a plus driver, a wire of which one end is integrally connected to the operation rod in the axial rotation direction, and a driving rod which is integrally connected to the other end of the wire in the axial rotation direction to be engaged with the crown gear. By using the operation unit, when the operation rod is operated to be axially rotated, the axial rotation is transferred to the driving rod as well through the wire, which enables the rotation of the crown gear engaged with the driving rod, and the aiming adjustment at a position spaced apart from the crown gear. Therefore, the workability is improved.